U0142

Code

LAND ROVER U — Network/User

Lost communication with the body control module B

Brand: LAND ROVER

Type: U — Network/User

Views: UK: 22 EN: 35 RU: 36

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Page language: EN

Causes

BCM B power supply fault (fuse, relay, battery connections)
BCM B ground open or high resistance
Damaged, corroded or disconnected BCM connector or harness
CAN bus short/open between BCM B and other modules
Missing or failed termination resistors on CAN bus
Interference or high resistance on CAN_H/CAN_L lines

Symptoms

Instrument cluster/network warning message(s) related to body module
Central locking, interior lighting, or convenience features inoperative or intermittent
Security/immobilizer warnings or inability to lock/unlock
Certain modules or systems report multiple CAN comms DTCs
Starting may be affected if BCM functions are required for crank/immobilizer
Intermittent behavior that changes with vibration or connector movement

What to check

Read all stored and pending codes on all control modules with a dealer-level or capable scan tool
Confirm freeze-frame and occurrence data (ignition state, voltage) when U0142 set
Verify battery voltage and charging system (12–14.5 V while running)
Check fuses and relays that feed BCM B and related circuits
Visually inspect BCM B connector and harness for corrosion, bent pins, water damage, or damage
Verify good chassis and module grounds (measure resistance to battery negative)

Signal parameters

Battery/ignition feed to BCM: ~12 V (cranking) to ~14.5 V (running)
CAN bus recessive voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each)
CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Termination resistance between CAN_H and CAN_L (with ignition off and modules disconnected if required): ≈ 60 Ω (two 120 Ω terminators in parallel)
Module ground resistance to battery negative: low, typically

Diagnostic algorithm

Connect an advanced scan tool and record all U-codes and module presence. Note freeze frame (ignition state, voltage).
Check battery voltage and charge state. Ensure 12+ V stable during tests; recharge if low.
Inspect BCM B fuses/relays and confirm power is present at the BCM connector (use wiring diagram to ID pins). Repair/replace blown fuses or faulty relays.
Inspect BCM connector and harness for corrosion, bent pins, water ingress, or chafed wires. Repair any damage; unplug and inspect both halves of connector.
Verify module ground(s): measure continuity from BCM ground pins to battery negative. Clean and tighten ground connections as needed.
Verify CAN physical layer: with ignition on, measure CAN_H and CAN_L voltages at the BCM connector. Confirm recessive ≈2.5 V each and proper dominant levels when bus is active. Measure termination resistance ≈60 Ω.
If CAN voltages are abnormal, isolate wiring: disconnect harness sections and check for short to battery/ground, open, or high resistance. Wiggle test harness while monitoring communications for intermittent faults.
If wiring and power/ground are good but BCM unresponsive, attempt to communicate to BCM with manufacturer tool and check for module firmware updates or reflash procedures. Follow OEM procedures for module wake and reprogramming.
If reprogramming fails and wiring/power/ground confirmed good, consider replacing BCM B per OEM instructions. After any repair, clear codes and road test to confirm fault does not return.
If intermittent, use data logging or back-probing while reproducing symptom; consider harness repair or protective routing to prevent recurrence.

Likely causes

Blown fuse or poor battery/ignition feed to BCM B
Poor ground at BCM B or nearby common ground point
Corroded/damaged BCM connector pins or wiring chafing
Open or shorted CAN_H or CAN_L between BCM and gateway/CAN backbone
Failed BCM (internal electronics) after other causes eliminated

Fault status

⚠️ Status

U0142 — Lost communication with Body Control Module B. The BCM B failed to respond to network requests. Check BCM power, ground, CAN bus wiring/termination, connectors, and module presence/firmware.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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U0142 — Lost communication with the body control module B